The invention concerns a screening device for sorting granular materials, with at least one rotatable rod basket located in the screening housing with turbo elements distributed across the circumference of the rotor and with inlets and outlets for screening gas, material to be screened, coarse material and fine material, whereby the outlet opening for the drawing-off of the screening gas flow charged with the fine material is located at least one of the narrow ends of the rotatable rod basket in the screening housing.
Such dynamic screening devices, also known as rod basket screening devices, where the material to be screened is accelerated to the circumferential velocity of the rod basket by the rotating rod basket in the screening zone, and the centrifugal force acting on the particles of the material to be screened and the frictional force of the air stream lead to the material to be screened being divided into coarse material and fine material are already known, e.g., described in “KHD Symposium '92”, Volume 1, 1993, by KHD Humboldt Wedag AG, paper by A. Süβegger Screening Report '92 page 63ff, particularly page 65, Fig. 1. The fine material is transported inwards by the air stream against the centrifugal force between the rods of the rod basket and leaves the screening device together with the screening air, whereas the centrifugal force pushes the coarse material to the outer edge of the screening device housing, where it is then transported downwards out of the screening zone by the force of gravity.
In the case of the known dynamic rod basket screening devices, the screening air stream charged with the fine material is routed via a more or less long pipeline to a separator such as a cyclone where the fine material is separated from the screening air. Accordingly, this requires space accordingly. In addition, the connecting pipeline between the rod basket screening device and downstream fine material separator causes a noticeable drop in pressure. This is also applicable even if the connecting pipeline between the rod basket screening device and a downstream cyclone separator is relatively short, as is the case with the known screening equipment DE-A 102 21 739.